Now, to the little girl who is fighting for her life after swimming in the lake. The 12-year-old from arkansas contracted a deadly disease in the water. And abc's ryan owens has all those details for us. Reporter: This perfectly healthy 12-year-old went for a summer swim. This morning, she's in the intensive care unit of an arkansas hospital, with a disease that kills 99% of people who contract it. Kaley got violently ill days after playing at this water park in a lake near little rock. Doctors diagnosed her with a rare meningitis caused by a parasi parasite. An amoeba that thrives in stagnant water. There's been 50 case of this disease reported in the last 10 years in the united states. But kaley is the second believed to be from this one lake. Three years ago, this 7-year-old boy died after swimming her. The owners have shut it down for the summer and maybe forever. It's hard for us to even think about the possibility of a child getting sick out here. Reporter: Scientists say only two americans have ever survived exposure to this amoeba. Her mom is praying kaley will be the third. We're hoping for kali to be number three. Reporter: Her mother is hoping to raise awareness. There's only one way to get this disease, to ingest contaminated water through the nose. The best way to prevent it, is to make kids wear nose plugs or hold their nose when they go under water. A simple tip from a mother whose daughter is fighting for her life. For "good morning america," ryan owens, abc news, dallas.

This transcript has been automatically generated and may not be 100% accurate.

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